What is the concept of the "Stop and frisk"?

A "stop and frisk," as the name implies, is a police procedure where an officer stops a person and, usually while questioning them, frisks their outer clothing to ensure that they are not carrying a concealed weapon. The standard for this search is "reasonable suspicion," which is obviously not as stringent a standard as "probable cause." The idea behind this practice is that police officers can use it as a preemptive measure to prevent a potential crime from occurring. The constitutionality of the "stop and frisk" was established by Terry v. Ohio in 1968, in which the US Supreme Court held that the interest the police had in attempting to prevent a crime from happening made a certain amount of latitude necessary and consistent with the Fourth Amendment's protection against unwarranted search and seizure. Subsequent decisions have generally strengthened the position that "stop and frisk" is a necessary tool for law enforcement.